This invention relates to improved AMS-1B crystalline molecular sieve-based catalyst compositions, and particularly, to the use of such compositions having improved ability to selectively isomerize xylene feeds.
In U.S. Pat. No. 4,532,226, a ZSM-5 aluminosilicate zeolite catalyst modified by P and Cr, Mo, or W and used to selectively catalyze formation of the 1,4-diakyl isomer during conversion of aromatic compounds is described. U.S. Pat. No. 4,518,703 teaches a P modified silica polymorph-based catalyst for the methylation of toluene. In U.S. Pat. Nos. 4,504,690, 4,128,592 and 4,086,287 is taught modifying a ZSM-5 aluminosilicate zeolite catalyst with P, Mg or P/Mg oxides to obtain high proportions of the 1,4-dialkyl isomer. Phosphorus modification of a ZSM-5 zeolite catalyst for the alkylation of toluene to form a higher proportion of p-xylene is shown in J. Appl. Polymer Sci. 36, 209 (1981) as are P or Mg modified ZSM-5 zeolite catalysts for the disproportionation of toluene. Selective para-alkylation using P modified ZSM-5 zeolite catalysts is again described in J. Cat. 67, 159 (1981). Conversion of olefins over the same type of catalyst is shown in J. Cat. 61, 155 (1980). Disproportionation of toluene to produce benzene and xylenes over P/Mg modified crystalline aluminosilicate zeolite catalysts is described in U.S. Pat. No. 4,137,195. Alkylation or disproportionation of certain monosubstituted benzene compounds to achieve nearly 100% selectivity to para-disubstituted derivatives over phosphorus compound-modified ZSM-5 aluminosilicate zeolite catalysts is reported in J. Am. Chem. Soc. 101, 6783 (1979).
Use of Mg compounds alone or in combination with P compounds to modify a ZSM-5 aluminosilicate of zeolite catalyst is described in U.S. Pat. No. 4,049,573 and the modified catalyst is used for converting alcohols and ethers to hydrocarbons. Again, magnesium is used to modify ZSM-5 zeolite catalysts in U.S. Pat. No. 4,002,698, which catalysts can be used for the selective production of p-xylene from charge stocks of toluene and a C.sub.3 -C.sub.10 olefin; P modified catalysts for the methylation of toluene are also described. Phosphorus modified ZSM-5 aluminosilicate zeolite catalysts are again described in U.S. Pat. No. 3,972,832 and described as useful for the conversion of aliphatics to various products.
Catalyst compositions, generally useful for hydrocarbon conversion, based upon AMS-1B crystalline borosilicate molecular sieve have been described in U.S. Pat. Nos. 4,268,420, 4,269,813, 4,285,919 and Published European Application No. 68,796.
As described in the references in the paragraph above, catalyst compositions typically are formed by incorporating an AMS-1B crystalline borosilicate molecular sieve material into a matrix such as alumina, silica or silica-alumina to produce a catalyst formulation. In one method of making AMS-1B crystalline borosilicate, sieve is formed by crystallizing sources for silicon oxide and boron oxide with sodium hydroxide and an organic compound. After crystallization, the resulting sodium form is ion exchanged with an ammonium compound and calcined to yield the hydrogen form of AMS-1B. In another more preferred method, AMS-1B crystalline borosilicate is crystallized in the hydrogen form from a mixture containing a diamine in place of a metal hydroxide. AMS-1B borosilicates in hydrogen form are designated HAMS-1B. Typically, the hydrogen form sieve is gelled with an alumina sol, dried and calcined to yield a catalyst composition.